1 Technical Field
This disclosure relates generally to an engine control apparatus which may be employed in automotive vehicles, and more particularly to such an engine control apparatus which is engineered to predict or calculate a rotational speed of an internal combustion engine within a period of time between start of a drop in speed of the engine resulting from stop of combustion of fuel in the engine and stop of revolution of the engine.
2 Background Art
Engine control systems for automotive vehicles are known which have an idle-stop function to monitor a driver's operation, such as an accelerating operation or a braking operation to start or stop the vehicle, to automatically stop or restart an engine mounted in the vehicle. Such automatic engine stop and restart control are usually done to reduce the consumption of fuel in the engine.
Japanese Patent First Publication No. 2014-77399 teaches an automatic engine stop and restart system which, when an engine restart request is made while the speed of the engine is decreasing in an automatic engine stop mode, restarts the engine as quickly as possible without waiting for complete stop of the engine. Specifically, when the engine restart request is made, the automatic engine stop and restart system works to predict the speed of the engine after a lapse of a period of time required to move a pinion of an engine starter and achieve mesh with a ring gear joined to an output shaft of the engine and then control the operation of the engine starter.
The above publication also teaches calculating a loss of energy during reverse rotation of the engine from a loss of energy during normal rotation of the engine to predict the speed of the engine in a reverse rotation range. In the prediction of the speed of the engine in the reverse rotation range, the loss of energy in a normal rotation range is broken down into a frictional component and a compression component. The positive and negative signs of the friction component are reversed, while the sum of the compression component over all strokes of the engine is assumed to be zero.
However, the assumption of the sum of the compression component over all the strokes of the engine as being zero in predicting the speed of the engine, however, results in a concern that the accuracy in predicting the speed of the engine decreases with an increase in compression component. The decreased prediction accuracy may result in a failure in meshing the pinion with the ring gear in an engine speed range permissible in terms of noise rising from the meshing of the pinion gear with the ring gear or mechanical wear of the pinion gear and the ring gear, which will lead to an increase in such noise or premature mechanical wear when the engine is restarted.